382 XXVIII. THE ANDKCECIUM OF ANGIOSPEBMS. 



stained cherry-red, the intine orange-red. The bright blue of 

 the former and orange-red of the latter stain are characteristic 

 of pectic substances, which latter constitute the greater proportion 

 of the intine. The intine in this case is so rich in pectic materials 

 that with chlorzinc iodine it gives clearly the .bright yellow pectic 

 reaction, and at any rate only its innermost homogeneous layer 

 shows an indistinct cellulose reaction. The intine of pollen-grains 

 always contains pectin, but otherwise the cellulose reaction is easy 

 to obtain in it. The exine, as always with cutinised membranes, 

 stains yellow-brown with chlorzinc iodine. Alcohol material of 

 the pollen of Hemerocallis fulva reacts even better than when 

 fresh. The oil is wanting in such preparations, since it is removed 

 by alcohol. Under the influence of sulphuric acid the structure of 

 the cutinised exine is still more clear. With a high magnifying 

 power it shows a delicate meandering network. In many meshes 

 of the exine we can see lying a blue body, with irregular outline, 

 which represents oil, previously yellow, but become blue in 

 sulphuric acid. The cutinised membrane itself has become 

 yellow ; after some hours it becomes reddish- brown, while the 

 extruded contents of the pollen-grain are stained rose-red, a 

 reaction which protoplasmic substances show under] the influence 

 of sulphuric acid and in the presence of sugar. In 25 per cent, 

 chromic acid the non-cutinised parts of the exine, and the con- 

 tents of the pollen-grain, are quickly dissolved ; the cutinised 

 parts resist its action longer. In its comparatively ready solu- 

 bility in chromic acid the substance of the exine differs from 

 corky and cutinised cell- walls, but it is nevertheless closely 

 related to suberin and cutin. 



Structure of the Anther Wall. We will now prepare cross- 

 sections through the anthers ; and first it would be well to turn 

 to a flowerrbud only about two-thirds grown, and cut cross- 

 sections through this. The sections of the perianth are then 

 removed from the preparation with the needles. Although we 

 have chosen so young a flower for investigation, we nevertheless 

 find all the pollen-sacs open. Their opening is effected very 

 easily, and in this case by the pressure of the razor in cutting. 

 The adjoining figure (Fig. 140, A) will help us to understand the 

 structure. The walls of the pollen-sacs break away (at p) from 

 the partitions separating the two sacs of each anther-lobe. Their 

 curvature is thus reduced. The two anther-lobes are joined 

 by the narrow connective, traversed by a vascular bundle (/). ,. 



